NAME

SYNOPSIS

DESCRIPTION

• A header file containing the C description of the data types necessary to encode the structures defined in ASN.1,
• An annotated ASN.1 file, suitable as an input to the MAVROS compiler,
• A C module containing the initialization of the C variables corresponding to the ASN.1 values declared in the module.
• A text file capturing the relation between types and values specified in ASN.1 "MACROS".

OPTIONS

• Specifying the name of the input file,
• Specifying the file location of modules refered to by the input,
• Specifying non default names for the output file,
• Parametrizing the C mappings,
• Requesting specific inputs.

• Specified as the first argument to MAVCOD, as in: "mavcod Module.asn1"
• or specified by using the -srce command line parameter, as in "mavcod -srce Module.asn1"

• Contain exactly one ASN.1 module definition,
• Have a file name composed of the module name and the suffix ".asn1".

ASN.1 is a modular language. A module may contain reference to types, values and macros defined in other modules. In order to compile properly the input module, MAVCOD must be able to read the specifications contained in the "imported" modules. This can be achieved by using the "-load asn1_files"option, as in:

• "mavcod Module.asn1 -load Imported-1.asn1 other-dir/Imported-2.asn1"

Note that if a module imports a MACRO definition, which by definition alters the regular ASN.1 syntax, the corresponding module must be explicitely loaded. Failure to do so would result in various "syntax error" reports.

By default, the names of the output files are constructed from the name of the module defined in the input file, e.g. "Module." The following options can be used to override this default behaviour:

• "-head header_name"
  Use the name header_name for the header file. By default, the name of the header file is constructed by appending the string _mvr.h to the name of the module, e.g. Module_mvr.h
• "-init c_file"
  Use the name c_file for the C file that will contain the initialization of ASN.1 values. By default, the name of the initialization file is constructed by appending the string _init.c to the name of the module, e.g. Module_init.c
• "-mvr mvr_name"
  Use the name mvr_name for the mavros input. By default, then name of the MAVROS input file is constructed by appending the string .mvr to the name of the module, e.g. Module.mvr
• "-macros text_file"
  Use the name text_file for the text file that will contain the "knowledge" extracted from the MACRO instantiations present in the module. By default, the name of this file is constructed by appending the string .macros to the name of the module, e.g. Module.macros The header file describes the mapping into C of the types defined in the ASN.1 input. This mapping is done according to simple rules, explained in the general MAVROS documentation. This rules can be parametrized by the following options:
• "-seqofsize number"
  By default, MAVCOD maps each ASN.1 list declaration (using the SEQUENCE OF or SET OF) construct to "length + pointer" C structure:
  struct {
  asn1_int32 n; /* number of elements */
  * v; }
  
• The pointer v will be allocated at decoding time to match the exact size required by the received message. However, as memory allocation is often a painful process, MAVCOD tries to replace this by a static declaration when the maximum size of the list is specified by use of a SIZE constraint, as in "SET SIZE(0..32) OF Foo", which would be mapped to:
  struct {
  asn1_int32 n; /* number of elements */
  Foo v[32]; }
  
• Some programmers have observed that this could result in very inefficient memory allocations when the maximum size is a very large number. By using the -seqofsize option, one can request that dynamic allocation be applied to lists which have a size greater than number. By specifying a value of 0, one can request that all list be dynamically allocated.
• "-octetsize n"
  This parameter plays for OCTETS STRING, BITS STRING and their subtypes, the same role that -seqofsize plays for lists.
• "-static" By default, MAVCOD uses dynamic memory allocation for optional components in a SET or SEQUENCE and for large components in a CHOICE. By specifying this parameter, one requests MAVCOD to use a static memory allocation whenever possible. For components of a SET or SEQUENCE, this static declaration will be complemented by the declaration of a boolean variable which will be set to TRUE (i.e. to a non null value) when the component is present.
• "-noflags" By default, MAVCOD represent BIT STRINGS wich have named elements, e.g.
  ColorsInHand ::= BIT STRING {
  Spade(0), Heart(1), Diamond(2), Club(3)}
  
• by a 32 bits integer variable where each bit can represent one of the elements of the string. By using the -noflags option, one can request that named bits strings be represented exactly as standard bits strings, i.e. by a length and a pointer field.
• nochars By default, MAVCOD represent character strings of known size by using the "null terminated string" convention of C. By using the -nochars option, one can request that these strings be represented exactly as standard octets strings, i.e by a length and a pointer field.
• keep This option is equivalent to the combination of -noflags and -nochars.
• compat This option instruct MAVCOD to use memory allocation procedures and octet string representations compatible with that used in the original version. It should be used when one wants to use the new version of the compiler and retain compatibility with previously developed software.
• iapl_V1 This option instruct MAVCOD to use type generation algorithms compatible with the initial release of this compiler. This is useful for developpers which have been using MAVCOD for a long time, may need to update existing ASN.1 modules, but don't want to update all their existing "C" interfaces.
• iapl_transview
  This option is similar to te previous one. It is used for maintaining compatibility with an intermediate release of the MAVCOD compiler.
• ser Prepare the generation by MAVROS of code for the "special encoding rules" defined by SNI.
• windows
  Generate an header file and an initialisation file which will be suitable for compiling under Microsoft's "Windows".

• "-asn1 asn1_file"
  Produce a pretty printing of the input, and place it in the named file. When this argument is used, MAVCOD will not generate the regular output files, unless they be explicitely requested.
• "-umac asn1_file"
  Remove all macro references from the input, and place a pretty printing of the resulting specification in the named file.
• "-indent string"
  Insert the string string instead of each tabulation mark in the various output files.

The MAVCOD program also supports a -check option, that is used for test programs. It produces on the standard output a concatenation of several pretty printings of the input at various stages of the analysis, of the header file, of the MAVROS input file, of the initialization file and of macro knowledge file.

"SEE ALSO"

DIAGNOSTIC

BUGS

The cross referencing of modules is hasardous: it supposes that exactly the same "C parametrization", e.g. that -static or -noflags were used in the different modules. One should be able to look at the definitions in the MAVROS inputs for these modules (*.mvr files), in order to extract the correct typing of the attributes.

Please report the other bugs to the authors..